1. Field of the Invention
This invention generally relates to an apparatus and method operative for electro-optically reading indicia having parts of different light reflectivity, for example, bar code or matrix array symbols, and, more particularly, to apparatus using both charge coupled device (CCD) technology and laser beam scanning technology for properly positioning, orienting and/or aiming such apparatus and reading one or two-dimensional bar code symbols, and to a method therefor.
2. Description of the Related Art
Various optical readers and optical scanning systems have been developed heretofore for reading indicia such as bar code symbols appearing on a label or on the surface of an article. The bar code symbol itself is a coded pattern of indicia comprised of a series of bars of various widths spaced apart from one another to bound spaces of various widths, the bars and spaces having different light-reflecting characteristics. The readers and scanning systems electro-optically transform the graphic indicia into electrical signals, which are decoded into alphanumerical characters that are intended to be descriptive of the article or some characteristic thereof. Such characters are typically represented in digital form and utilized as an input to a data processing system for applications in point-of-sale processing, inventory control, and the like. Scanning systems of this general type have been disclosed, for example, in U.S. Pat. Nos. 4,251,798; 4,369,361; 4,387,297; 4,409,470; 4,760,248; 4,896,026, all of which have been assigned to the same assignee as the instant application.
As disclosed in some of the above patents, one embodiment of such a scanning system resides, inter alia, in a hand-held, portable laser scanning head supported by a user, which is configured to allow the user to aim the head, and more particularly, a light beam, at a target and a symbol to be read.
The light source in a laser scanner bar code reader is typically a gas laser or semiconductor laser. The use of semiconductor devices as the light source in scanning systems is especially desirable because of their small size, low cost and low voltage requirements. The laser beam is optically modified, typically by a focusing optical assembly, to form a beam spot of a certain size at the target distance. It is preferred that the cross section of the beam spot at the target distance be approximately the same as the minimum width between regions of different light reflectivity, i.e., the bars and spaces of the symbol.
The bar code symbols are formed from bars or elements typically rectangular in shape with a variety of possible widths. The specific arrangement of elements defines the character represented according to a set of rules and definitions specified by the code or xe2x80x9csymbologyxe2x80x9d used. The relative size of the bars and spaces is determined by the type of coding used, as is the actual size of the bars and spaces. The number of characters per inch represented by the bar code symbol is referred to as the density of the symbol. To encode a desired sequence of characters, a collection of element arrangements are concatenated together to form the complete bar code symbol, with each character of the message being represented by its own corresponding group of elements. In some symbologies, a unique xe2x80x9cstartxe2x80x9d and xe2x80x9cstopxe2x80x9d character is used to indicate where the bar code begins and ends. A number of different bar code symbologies exist. These symbologies include UPC/EAN, Code 39, Code 128, Codabar, and Interleaved 2 of 5, etc.
For the purpose of our discussion, characters recognized and defined by a symbology shall be referred to as legitimate characters, while characters not recognized and defined by that symbology are referred to as illegitimate characters. Thus, an arrangement of elements not decodable by a given symbology corresponds to an illegitimate character(s) for that symbology.
In order to increase the amount of data that can be represented or stored on a given amount of surface area, several new bar code symbologies have recently been developed. One of these new code standards, Code 49, introduces a xe2x80x9ctwo-dimensionalxe2x80x9d concept by stacking rows of characters vertically instead of extending the bars horizontally. That is, there are several rows of bar and space patterns, instead of only one row. The structure of Code 49 is described in U.S. Pat. No. 4,794,239, which is incorporated herein by reference. Another two-dimensional symbology, known as xe2x80x9cPDF417xe2x80x9d, is described in U.S. patent application Ser. No. 461,881, now U.S. Pat. No. 5,304,786. Still other symbologies have been developed in which the symbol is comprised of a matrix array made up of hexagonal, square, polygonal and/or other geometric shapes. Prior art FIGS. 24A-24C depict exemplary known matrix and other type symbols. Such symbols are further described in, for example, U.S. Pat. Nos. 5,276,315 and 4,794,239. Such matrix symbols may include Vericode(TM), Datacode(TM) and UPSCODE(TM).
In the laser beam scanning systems known in the art, the laser light beam is directed by a lens or similar optical components along a light path toward a target that includes a bar code or other symbol on the surface. The moving-beam scanner operates by repetitively scanning the light beam in a line or series of lines across the symbol by means of motion of a scanning component, such as the light source itself or a mirror, disposed in the path of the light beam. The scanning component may either sweep the beam spot across the symbol and trace a scan line or pattern across the symbol, or scan the field of view of the scanner, or do both.
Bar code reading systems also include a sensor or photodetector which functions to detect light reflected or scattered from the symbol. The photodetector or sensor is positioned in the scanner in an optical path so that it has a field of view which ensures the capture of a portion of the light which is reflected or scattered off the symbol is detected and converted into an electrical signal. Electronic circuitry or software decode the electrical signal into a digital representation of the data represented by the symbol that has been scanned. For example, the analog electrical signal operated by the photodetector may be converted into a pulse width modulated digital signal, with the widths corresponding to the physical widths of the bars and spaces. Such a digitized signal is then decoded based upon the specific symbology used by the symbol into a binary representation of the data encoded in the symbol, and subsequently to the alphanumeric characters so represented.
The decoding process in known bar code reading systems usually works in the following way The decoder receives the pulse width modulated digital signal from the bar code reader, and an algorithm implemented in software attempts to decode the scan. If the start and stop characters and the characters between them in the scan were decoded successfully and completely, the decoding process terminates and an indicator of a successful read (such as a green light and/or an audible beep) is provided to the user. Otherwise, the decoder receives the next scan, performs another decode attempt on that scan, and so on, until a completely decoded scan is achieved or no more scans are available.
Such a signal is then decoded according to the specific symbology into a binary representation of the data encoded in the symbol, and to the alphanumeric characters so represented.
Moving-beam laser scanners are not the only type of optical instrument capable of reading bar code symbols. Another type of bar code reader particularly relevant to the present invention is one which incorporates detectors based upon charge coupled device (CCD) technology. In such prior art readers the size of the detector is typically smaller than the symbol to be read because of the image reduction by the objective lens in front of the CCD. The entire symbol is flooded with light from a light source such as light emitting diodes (LED) in the reader, and each CCD cell is sequentially read out to determine the presence of a bar or a space.
The working range of CCD bar code scanners can be rather limited as compared to laser based scanners and is especially low for CCD based scanners with an LED illumination source. Other features of CCD based bar code scanners are set forth in parent applications Ser. Nos. 317,553 and 717,771 which are hereby incorporated by reference, and which are illustrative of the earlier technological techniques proposed for use in CCD scanners to acquire and read two-dimensional indicia.
It is a general object of the present invention to provide an improved indicia scanner without the limitations of prior art readers.
It is a further object of the present invention to provide an indicia scanner capable of providing the features of both a flying spot light beam scanner and an imaging scanner in a single unit.
It is a still further object of the present invention to provide a scanner for reading both two-dimensional or more complex indicia and linear bar codes.
It is yet another object of the invention to provide a handheld indicia reader that is capable of aiming or being oriented and also imaging the field of view.
It is still another object of the invention to both perform laser scanning and CCD imaging either simultaneously, alternatively, or on a time-division multiplexed basis.
It is also an object of the invention to provide an indicia reader capable of automatically and adaptively reading indicia of different symbology types, including indicia comprised of a matrix array of geometric shapes such as a UPSCODE(TM), in close spatial proximity.
It is an even further object of the invention to provide a method which can be used to accomplish one or more of the above objectives.
Additional objects, advantages and novel features of the present invention will become apparent to those skilled in the art from this disclosure, including the following detail description, as well as by practice of the invention. While the invention is described below with reference to preferred embodiments, it should be understood that the invention is not limited thereto. Those of ordinary skill in the art having access to the teachings herein will recognize additional applications, modifications and embodiments in other fields, which are within the scope of the invention as disclosed and claimed herein and with respect to which the invention could be of significant utility.
According to the present invention a scanning device for scanning or reading indicia of differing light reflectivity, such as bar code or matrix array symbols containing optically encoded information, is provided. The scanning device has a single light emitter, preferably including a laser or light emitting diode, for generating a scanning light beam to visually illuminate sequential portions of the indicia and produce reflected light from the indicia. A sensor, such as a linear array of a charge coupled device or two-dimensional array of a solid state imaging device simultaneously detects light from the light beam or ambient light reflected from portions of the indicia and generates an electrical signal representative of the reflected light from the portions of the indicia. The sensor may operate in either a scanning or non-scanning mode, the latter being similar to that of a single photodetector, or in both modes. When operating in a scanning mode, the sensor may scan a field of view at a rate faster or substantially slower than the scanning light beam. The sensor may be controlled to scan a field of view only periodically and may function as a range detector to detect the distance between the scanning device and targeted indicia. The sensors"" operation as a range detector is further described below. The emitter and sensor may be disposed in a hand-held housing to allow for portable operation.
According to other aspects of the invention, the scanning device may also include an ambient light sensor for detecting the level of the ambient light in a field of view and producing an output signal if the ambient light is above a threshold value, i.e. the value at which sufficient ambient light exist for a satisfactory read of the indicia without additional light being reflected from the indicia. An activator can also be included to activate the emitter, preferably automatically, in response to the output signal. The activator may also be responsive to the electrical signal generated by the sensor. In this way, the emitter is activated, for example, only after the sensor has obtained a satisfactory read on one symbol and the emitter continues to emit a light beam until the sensor has obtained a satisfactory read of the next symbol. Unlike some prior art bar code readers, the light beam need not be deactivated after a successful decode of a symbol. More particularly, the light beam could be deactivated only if no decode had taken place after a predetermined time.
A processor for processing the electrical signal is also preferably provided. The processor typically includes an analog to digital converter for converting the electrical signal into a corresponding digital signal, and a decoder for decoding the digital signal in order to obtain the information encoded within the symbol. The processor may include a discriminator for determining whether the targeted symbol is a linear or multidimensional symbol, or a bar code symbol of a certain symbology type. A selection device is beneficially provided for deactivating the light emitter if it is determined that the targeted symbol is a multidimensional bar code symbol. The discriminator may be adapted to more generally discriminate between indicia of different symbology types or to discriminate between indicia of any desired symbology types. For example, the discriminator may be adapted to look for symbols conforming to UPSCODE(TM). The sensor can be adapted to detect visible light reflected from a portion of the symbol which is formed of a bull""s eye mark. Such marks are being more frequently used in conjunction with symbols formed of a matrix array of geometric shapes, such as those conforming with UPSCODE(TM) symbology.
In a second embodiment of the invention for reading indicia of the types described above, a scanning device is provided with a first light emitter, for example a light emitting diode, which generates a light beam directed along a path toward the indicia, say a bar code symbol, so as to illuminate a field of view including the indicia. A second light emitter, such as a laser diode, generates a scanning light beam to visually illuminate sequential portions of the symbol so as to produce reflected light from the indicia. A sensor, preferably a linear charge coupled or two-dimensional solid state imaging device, senses or images the reflected light and generates an electrical signal responsive to the detected light indicative of the indicia. The light from the first light emitter is thus used only for aiming or orienting the scanning device. If desired, the first and second light emitters can be disposed in the same housing. The linear charge coupled device is beneficially arranged within the scanning device so that the elongated dimension of the charge coupled device is parallel to the scanning light beam.
According to other aspects of this second embodiment, a ambient light sensor identical in function to that described above may also be provided. An activator to activate one or both of the light emitters responsive to the output signal of the ambient light sensor is beneficially included as part of the scanning device. The activator may also be made responsive to the electrical signal, as discussed previously in the context of the first embodiment. The scanning device may also include a processor like that described above, including converter, decoder, discriminator, selection device and other features of the processor described above. The sensor can, likewise, be adapted to detect visible light reflected from a portion of the symbol which is in the form of a bull""s eye mark.
In accordance with yet another embodiment of the invention, a scanning device for reading indicia, such as that previously described, having parts of different light reflectivity has a light source, such as a laser or light emitting diode, for generating a visible light beam. An optical element, preferably a mirror, directs the visible light beam such that a scan line is formed across the indicia. A sensor, preferably a charge coupled or other solid state imaging device, which includes an array of detection elements, images the reflection of light from the indicia, for example visible light from the visible light beam or ambient light, or a combination of the two, and generates an electrical signal representing the reflection of the light from the indicia or, stated another way, the spatial intensity variations of the indicia. The individual detection elements can be scanned at a variable scanning rate if desired. An actable controller can be provided to change the element scanning rate as desired. The scanning device may also include an integrator for processing the output of the individual detection elements to produce a single output signal. Preferably, auto-focus optics to receive the reflected light and adjust the focal point of the image on the array of detection elements are also provided. Processing circuitry for processing an electrical signal generated by the sensor may be provided. The circuitry may include a determining means which determines if the targeted indicia is a matrix code or bar code symbol, or of other differing symbology types, such as a linear or multidimensional symbol. A selection means deactivates the light emitter and/or the sensor if it is determined by the determining means that the symbol is of a particular symbology type, for example a bar code of certain symbology category.
This embodiment is particularly suitable for reading indicia, such as a bar code symbol, located within a range of approximately four to ten inches from the scan head of the scanning device. The light source, optical element and sensor can be beneficially housed in a light weight portable housing. The housing may also include an actuable controller as well as a wireless transmitter for transmitting information to a remote receiver.
The scanning device in accordance with this later embodiment may also include any or all of the other features, or be adapted to perform any or all of the other functions, discussed above in connection with the other described embodiments of the invention.
Additionally, in accordance with other aspects of this later embodiment, a photodetector, such as a photodiode, for detecting the reflection of light from the visible light beam off the indicia may be provided. With the photodetector incorporated in the scanning device, the sensor is beneficially used to detect either ambient light or light from the light beam reflected off one portion of the indicia, or is utilized to estimate the distance or range between the radii and the target, while the photodetector is used to detect light from the scanning light beam reflected off another portion of the indicia. Such an arrangement is particularly beneficial when the indicia is comprised of two adjacent or otherwise proximately located symbols. For example, the sensor may be used to detect reflected light from a matrix array symbol, perhaps one conforming to UPSCODE(TM), and he photodetector used to detect a one dimensional bar code symbol.
According to still further aspects of this later embodiment, the scanner can be adapted to operate in two or more distinct modalities, for example one for reading symbols of one symbology type such as stacked or other adjacent rows of linear bar codes, and the other for reading symbols of a different symbology type, such as matrix codes.
If two modalities are required, the scanner preferably includes two symbol discriminators one of which is adapted to determine if the symbol is of one predetermined category or symbology type and the other adapted to determine if the symbol is of another predetermined category. A signal is generated by one symbol discriminator if the symbol being imaged by the sensor does not conform to one of the symbology types. The sensor is deactivated in response to this signal. A signal is generated by the other symbol discriminator if the symbol detected by the photodetector does not conform to the other of the symbology types. The photodetector is deactivated in response to this signal. By directing both the sensor and photodetector to the same targeted symbol, the category of the targeted symbol is thereby indicated, since the symbol necessarily conforms to the predetermined symbology type acceptable to the symbol discriminator which does generate a signal to deactivate its associate detector. If both discriminators generate signals then the category of the targeted signal is necessarily outside the or determined categories for the scanner. Either of the two modalities are therefore automatically selected in response to a signal received from one of two symbol discriminators. Thus, for example, in one modality a charge coupled device is activated to read matrix codes by imaging and in the other modality a photodiode is activated to read bar codes using light from a flying spot light beam or laser line reflected off the symbol.
In accordance with still other aspects of the invention as embodied in this later embodiment, the same sensor or, a second sensor is provided for ranging. The sensor senses the change in the image produced by the scanned visible light beam as the separation distance between the indicia and the scanning device is increased or decreased. The sensor also generates an electrical signal indicative of the separation distance. Preferably the sensor is a position sensitive sensor or an array of detection elements.
In accordance with the scanning method of the present invention, a scanning light beam, preferably a visible laser light beam, is generated by a single light source to visually illuminate sequential portions of the indicia in order to produce reflected light from the indicia. The light reflected from portions of the indicia, which may be ambient light or light from the light beam, is simultaneously sensed preferably using an imaging technique. The sensing may include detecting visible light reflected from a portion of the indicia which is in the form of a bull""s eye mark. The sensing may be performed only periodically. Additionally, ranging may also be performed to determine the distance to indicia. An electrical signal representative of the detected light reflected from the portions of the indicia is generated.
According to other aspects of the inventive method, the level of the ambient light in a field of view is detected and an output signal is produced if the ambient light is above a threshold value. The light beam is generated responsive to the output signal. Beneficially, the light beam can also be generated responsive to the electrical signal.
The electrical signal may be processed to obtain an indication of the type of indicia being scanned. Thus, the processing may include a first threshold of determining whether the indicia is a linear or multidimensional symbol, or a bar code symbol of a particular symbology type, and generating the scanning light beam only if the bar code symbol is determined to be a linear bar code symbol. The processing can also include generating and processing a digitized signal corresponding to the electrical signal. The processing may include discriminating between indicia of different symbology type""s, linear, two-dimensional or stacked bar codes, matrix codes, or other types of indicia patterns.
According to another method of the present invention, two light beams are generated. One of the beams is directed so as to illuminate the entire indicia simultaneously and produce first reflected light from the indicia. The other beam, preferably a laser light beam, is directed so as to scan the field of view, that is, to visually illuminate spatially sequential portions of the indicia and produce second reflected light from the indicia. The two light beams may be directed to different parts of the target so that the reflected light from each distinct part can be distinguished. Alternatively, if the target area is small, the two light beams can be time division multiplexed, so that only one beam is active at a given time. The first reflected light is sensed, preferably by an imaging technique, and an electrical signal is generated representing the sensed light. The sensing or imaging may include detecting visible light reflected from a portion of the indicia which is in the form of a bull""s eye mark. The light from the second beam, i.e. the scanned beam, may be detected by a single detector, or the same sensor used to detect the first beam, except the sensor is not operated in the scanning mode.
According to other beneficial aspects of this second method, the level of ambient light in a field of view is detected and an output signal is produced if the detected ambient light level is above a threshold value. Either or both light beams are, as desired, generated or modified responsive to the output signal. The electrical signal may be processed to obtain information represented by the indicia. It may also be desirable for the light beams to be generated responsive to the electrical signal. Processing typically includes converting the analog electrical signal into a corresponding digital signal and decoding the digital signal. The processing can, if desired, include discriminating between indicia of different symbology types.
In a third method according to the present invention, a visible light beam, preferably a laser light beam, is generated and directed such that it forms a scan line across said indicia. The indicia is sensed, preferably using an imaging technique, so as to sense a reflection of light from the indicia. The detected light may be, for example, reflected ambient light or visible light from the light beam. The sensing may include detecting light reflected from a portion of the indicia which is in the form of a bull""s eye mark. One or more electrical signals representing the reflection of the light from the indicia is generated. If multiple electrical signals are generated, it may be desirable to process these signals to produce a single output signal. It may also be beneficial to focus, automatically, the light reflected from the indicia prior to sensing. This method is particularly suitable for reading indicia within a range of approximately four to ten inches from the scanning device. Preferably, signals corresponding to the electrical or output signal are transmitted by a wireless transmitter or transceiver to a remote receiver or transceiver.
According to other aspects of the third inventive method, ambient light levels in a field of view are detected and an output signal generated if the detected ambient light is above a threshold value. The light beam is generated in response to the output signal. The electrical signal is typically processed. Processing can include converting the analog electrical signal to a corresponding digital signal, and decoding the digital signal to obtain optically encoded information represented by the indicia. The decoding may include discriminating between indicia of different symbology types, for example, a bar code and a matrix array of geometric shapes, such as a UPSCODE(TM). It may also be beneficial to generate the light beam responsive to the electrical signal so that activation occurs only when necessary and appropriate for obtaining a read.
In accordance with further aspects of the third method of the invention, the reflection off one portion of the indicia of light from the visible light beam is photodetected while reflection off another portion of the indicia of either ambient light or light from the light beam is sensed. This method is particularly beneficial for use with indicia which include two symbols, for example a bar code and a matrix array symbol, disposed adjacent or in close proximity to each other.
According to still other aspects of the third method of the present invention, the scanner or reader operates in two distinct modalities, one for reading symbols of one symbology type or category, such as bar code symbols and the other reading symbols of a different symbology type or category, such as matrix codes. The scanner determines if the symbol being targeted is of one of the predetermined category or symbology types. A signal is generated which indicates the category of the targeted symbol and the modality is selected in response to the generated signal to subsequently read a symbol. Either of the two, or more, modalities can be selected in response to the generated signal. In one modality a charge coupled device may read matrix codes by imaging and in the other modality bar codes, such as stacked bar codes or adjacent rows of linear bar codes, may be read using light from a flying spot light beam or laser line reflected off the symbol or indicia.
According to still further aspects of this third method, range finding is performed. Range finding is accomplished by sensing the change in an image produced by the visible light beam while increasing or decreasing of the separation distance between the indicia and the scanning device. An electrical signal can then be generated which is indicative of the separation distance.